Project Summary/Abstract Children living in the United States are frequently exposed to polybrominated diphenyl ethers (BDEs) and organophosphate-based compounds (OPFRs) that are used as flame retardants in consumer goods. While the effects of BDE exposure on children?s neuro-cognitive and behavioral development has been studied, there is a lack of data on the developmental effects of OPFR exposure. Yet, toxicological data suggests that OPFRs may be more neurotoxic than BDEs. Animal models also show that social experiences have the potential to attenuate or buffer the effects of neurotoxic chemicals on neuro-cognitive and behavioral outcomes. Therefore, we propose a new interdisciplinary study that will improve our understanding of children?s exposures to flame retardant compounds, as well as, examine the interplay between flame retardants and adverse social experiences on children?s neuro-cognitive, executive functioning, and behavioral development. We propose to recruit 600 children aged 4-8 years as they enter preschool and follow them for 3 years until they graduate from first grade. The development that occurs during this time period is sizeable and corresponds with neural development associated with self-regulation of attention, emotion, and behavior. We will conduct repeated measurements during this follow up period to accomplish the following aims: (1) assess exposure to OPFRs and BDE among a diverse group of children to improve our understanding of factors that contribute to inter- and intra- individual variability, (2) examine the exposure-response relationship between OPFRs and children?s development between ages 4-8 years, and examine the potential for sex to modify these associations, and (3) examine the moderating influences of social stressors on the association between flame retardant exposures and children?s development. These aims all revolve around a central hypothesis that children with higher exposure to OPFRs and/or BDEs and will show lower neuro-cognitive, social, and behavioral skills. Completion of the proposed research is expected to provide new data on the human effects associated with flame retardant chemicals that are commonly found in the indoor environment. This data can be used to inform multi-pronged public health interventions that would ultimately improve children?s health and development.